Method and apparatus for electrostatic dispensing of microdroplets

Abstract

An apparatus and device for dispensing femtoliter to nanoliter volumes of liquid samples are disclosed. The apparatus includes a liquid-support plate, two electrodes, a substrate, and a control unit. The liquid support plate has a plurality of liquid-support regions, each capable of supporting a liquid meniscus thereon. The first electrode contains a plurality of electrode connections, each operatively connected to one of the liquid support regions, for electrical contact with a meniscus supported in such region. The substrate has a first side confronting the plate and an opposite side, and a plurality of sample-holding regions formed in the first side. The second electrode is disposed adjacent one of the two substrate sides. Thus, a selected volume of the liquid can be ejected from or to one or more of the liquid-support regions to or from one or more of the sample-holding regions.

1. Apparatus for use in dispensing a selected volume of each of a plurality of liquid samples, comprising
 a liquid-support plate having a plurality of liquid-support regions, each capable of supporting a liquid meniscus thereon,  
 a first electrode containing a plurality of electrode connections, each operatively connected to one of said liquid support region, for electrical contact with a meniscus supported in such region,  
 a substrate having a first side confronting said plate and a plurality of sample-holding regions formed in said first side,  
 a second electrode disposed between said liquid-support plate and said substrate, said second electrode defining an electrode gap adapted to accommodate movement of a liquid droplet ejected from a liquid-support region to a sample region, and  
 a control unit including a power source for applying a voltage potential across the two electrodes, thereby to eject a selected volume of the liquid from one or more of said liquid-support regions to one or more of said sample-holding regions.  
 
     
     
       2. The apparatus of  claim 1 , for use in dispensing a selected volume in the femtoliter to nanoliter volume range, wherein the voltage potential applied across the two electrodes has a pulse amplitude or change in pulse amplitude between 0.1-5 kV, and a selected pulse duration in the range 0.1 to 500 msec. 
     
     
       3. The apparatus of  claim 2 , wherein said control unit is operable to apply across said first and second electrodes, a voltage potential with a selected pulse duration between about 1-100 msec. 
     
     
       4. The apparatus of  claim 1 , wherein the spacing between said meniscus and said second electrode is between about 0.1-5 mm. 
     
     
       5. The apparatus of  claim 1 , wherein said liquid-support plate and substrate can be positioned with respect to one another to place each liquid-support region in alignment with a corresponding substrate sample-holding region, creating pairs of aligned liquid-support regions and sample regions. 
     
     
       6. The apparatus of  claim 5 , wherein said second electrode includes a single electrode gap which is relatively movable, with respect to said plate and substrate, to place the electrode gap in alignment with pairs of aligned liquid-support regions and sample regions. 
     
     
       7. The apparatus of  claim 6 , wherein said control unit is operable to move said electrode gap successively to adjacent aligned pairs of liquid-support regions and sample regions, and to apply said voltage potential pulse at each successive aligned pair. 
     
     
       8. The apparatus of  claim 5 , wherein said liquid-support plate, second electrode and substrate are all independently movable with respect to the other, under the control of said control unit. 
     
     
       9. The apparatus of  claim 1 , wherein said control unit is operable to apply such voltage potential to said first-electrode connections simultaneously. 
     
     
       10. The apparatus of  claim 1 , wherein said control unit is operable to apply such voltage potential to said first-electrode connections sequentially. 
     
     
       11. The apparatus of  claim 5 , wherein said second electrode includes an electrode plate having a plurality of electrode gaps adapted to be positioned with respect to liquid-support plate so as to position each gap in alignment with an associated first-electrode connection. 
     
     
       12. The apparatus of  claim 11 , wherein said liquid-support plate and said second-electrode plate are relatively movable, as a unit with respect to said substrate. 
     
     
       13. The apparatus of  claim 11 , wherein said control unit is operable, when the second electrode gaps are positioned between corresponding pairs of aligned liquid-support regions and substrate sample regions, to apply such voltage-potential pulse simultaneously to all or a selected one or more of the aligned first-electrode connections and second-electrode gaps. 
     
     
       14. The apparatus of  claim 11 , wherein said control unit is operable, when the second electrode gaps are positioned between corresponding pairs of aligned liquid-support regions and substrate sample regions, to apply such voltage-potential pulse sequentially to all or a selected one or more of the aligned first-electrode connections and second-electrode gaps. 
     
     
       15. The apparatus of  claim 1 , wherein each sample-holding region in said substrate includes a defined-size hydrophilic region surrounded by a hydrophobic surface area. 
     
     
       16. A method of transferring a selected volume of each of a plurality of selected aqueous, organic, or aqueous/organic liquid samples, comprising
 adding a liquid sample to one or more of the liquid-support regions in the liquid-support plate in the apparatus of  claim 1 ,  
 positioning the liquid-support plate in said apparatus with respect to the substrate so as to align one or more of the plate liquid-support regions with one of more of the substrate sample-holding regions,  
 placing the electrode gap in the second electrode in the apparatus between the liquid-support plate and the substrate, and oppositioned therein to accommodate movement of a liquid droplet ejected from a liquid-support region to a sample-holding region, and  
 applying a voltage potential across the first and second electrodes in the apparatus, thereby to eject a selected volume of the liquid from one or more of said liquid-support regions to one or more of said sample-holding regions.  
 
     
     
       17. The method of  claim 3 , wherein said applying is with a selected pulse duration between about 1-100 msec. 
     
     
       18. The method of  claim 16 , for use in dispensing a selected volume in the femtoliter to nanoliter volume range, wherein the voltage potential applied across the two electrodes has a pulse amplitude or chance in pulse amplitude between 0.1-5 kV, and a selected pulse duration in the range 0.1 to 500 msec. 
     
     
       19. The method of  claim 16 , wherein said positioning is effective to place each liquid-support region in alignment with a corresponding substrate sample region, creating pairs of aligned liquid-support regions and sample regions. 
     
     
       20. The method of  claim 19 , wherein the second electrode includes a single electrode gap which is relatively movable, with respect to said plate and substrate, to place the electrode gap adjacent pairs of aligned liquid-support regions and sample regions, and said placing and applying is effective to move the second electrode successively to adjacent aligned pairs of liquid-support regions and sample regions, and to apply said voltage potential pulse at each successive aligned pair. 
     
     
       21. The method of  claim 16 , wherein said applying is operable to apply a voltage potential to all or a selected one or more of the first-electrode connections. 
     
     
       22. The method of  claim 19 , wherein said second electrode includes an electrode plate having a plurality of electrode gaps adapted to be positioned with respect to liquid-support plate so as to position each gap in alignment with an associated first-electrode connection, and said applying is effective to apply said voltage potential to a selected one or more of said first-electrode connections. 
     
     
       23. The method of  claim 16 , wherein said applying is operable to simultaneously eject a sample from one or more of the plurality of liquid-support regions to the corresponding aligned sample-holding region or regions. 
     
     
       24. The method of  claim 16 , wherein said applying is operable to sequentially eject a sample from one or more of the plurality of liquid-support regions to the corresponding aligned sample-holding region or regions. 
     
     
       25. Apparatus for use in dispensing a selected volume of a liquid onto each of a plurality of regions on a substrate, comprising
 structure defining a liquid-support region,  
 a first electrode operatively connected to a liquid support region, for electrical contact with a meniscus supported in such region,  
 a second electrode carried on said structure and defining an electrode gap aligned with said liquid-support region to accommodate movement of a liquid droplet ejected from the liquid-support region onto such a substrate, and  
 a control unit including a power source for applying a voltage potential across the two electrodes, thereby to eject a selected volume of the liquid from said liquid-support region onto such a selected region on such a substrate.  
 
     
     
       26. The apparatus of  claim 25 , for use in dispensing a selected volume in the femtoliter to nanoliter volume range, wherein the voltage potential applied across the two electrodes has a pulse amplitude or change in pulse amplitude between 0.1-5 kV, and a selected pulse duration in the range 0.1 to 500 msec.